Biopolymer templated porous TiO2: An efficient catalyst for the conversion of unutilized sugars derived from hemicellulose

Abstract

An efficient procedure for the conversion of unutilized abundant sugar derivatives, such as d-mannose, d-galactose and lactose, into platform molecule 5-hydroxymethylfurfural in aqueous and organic medium is reported. This process involves biopolymer sodium alginate templated porous TiO2 nanocatalysts containing strong Lewis acidic sites as determined by pyridine-IR and temperature programmed desorption (TPD) of ammonia studies. Porous TiO2 materials were characterized by XRD, SEM, HR-TEM and N2 sorption techniques. Biopolymer templating pathway provided effective synthetic route for the TiO2 nanomaterials, which contain considerable mesoscopic void space as revealed from the HR-TEM and N2 sorption studies. Using this TiO2 catalyst, improved HMF yields were obtained without using expensive ionic liquids as solvents. Hydrothermally obtained TiO2 nanocatalysts showed maximum activity in d-mannose conversion to HMF, whereas nonporous TiO2 is inactive in this reaction. Porosity (surface area), small particle size and strong acidic sites generated through biopolymer templating pathway are crucial for high catalytic activity.